50/125- Multimode fiber size, 50-micron core and 125 micron cladding diameters. Standard in European Union, also specified for high bandwidth Gigabit Ethernet installations using laser transmitters at 850nm.

62.5/125- Multimode fiber size, 62.5-micron core and 125 micron cladding diameters. Standard in USA.

9/125- Singlemode fiber size, 7 to 9 micron core and 125 micron cladding diameters.

900 micron-Term for fiber cable with one fiber strand within a 900-micron diameter plastic jacket. Also known as a "tight tube" fiber cable. Fiber strands within zip cord and distribution cable types will be 900-micron fibers.

Access control- Electronic security system that monitors and controls entry and egress from a building. May be integrated with CCTV, personnel badging, door hardware, and other functions.

Adapter- Interfacing device to hold two connectors together with a minimum of signal loss. Also called "barrels".

Add-drop multiplexer- Optoelectronic device that can both transmit and receive signals. Generally connected to a pair of fibers. Specific signals can be "added" to the fiber link, and/or signals can be "dropped" to the device, and converted into their electrical component.

Adulterants - Molecules of foreign substances that become included in a fiber core during the manufacturing process.

Alcohol Wipes- Pre-packaged wipes impregnated with high purity alcohol. Used to clean fibers before cleaving, splicing, or connector installation.

Alignment post- Protrusion on connector body that fits into a slot in the adapter, which keeps the connector face from rotating in the adapter.

All dialectric- A cable that has no metal elements. This cable cannot conduct electricity, and does not require grounding when entering a building from the outside.

Analog- Communication signals transmitted as continuously fluctuating values, usually in the form of a "sine" wave. Typically used in CCTV, and local telecommunications.

Angled Physical Contact ("APC")- Type of connector having an 8-degree angle on the face. These connectors normally have a green colored body, and cannot be connected to non-APC connectors. Used in high bandwidth singlemode systems to reduce back reflection.

Aramid yarn- Yellow string-like material used as a strength member in most types of fiber cable construction. Also known by the trademarked name "Kevlar", this is the same material used to make bulletproof vests and helmets. A very strong material that does not stretch, the aramid yarn is often used to pull a fiber cable through a conduit.

Attenuation- Reduction in power of a light signal from the transmitter to the receiver or end of the fiber link. Also called "optical loss", attenuation is measured in decibels (dB's).

Attenuators- Devices that add loss to a fiber system when a reduction in light power is needed for proper optoelectronic receiver function. Attenuators can be fixed, providing a constant loss value at certain wavelengths, or adjustable.

Back reflection- Light signals that are returned to the optoelectronic transmitter. These reflections are caused by mechanical splices, mated connector pairs, and Rayleigh scattering.

Backbone- In a standardized structured cabling network, the backbone is a high capacity cable(s) which connect the main computer room (Main Cross Connect) to the substations, or "Telecommunications Closets". Backbone cabling is usually multimode or singlemode fiber, based on the distances and desired bandwidth capacity.

Backscatter area- The gradually downward sloping line on an OTDR trace or display. This part of the trace can be analyzed for the quality of the fiber and/or installation.

Bandwidth- The volume of signaling information that can be simultaneously sent through a particular medium, such as fiber, copper, or wireless.

Barrel- Interfacing device to hold two connectors together with a minimum of signal loss. Also called "adapters".

Bend radius violation- Excessive bending of a fiber cable during or after installation.

Bi-directional testing- Performing a test on a fiber link from both directions.

Bit error rate ("BER")- Measurement of errors in the digital transmission of information, such as in a high bandwidth computer network.

Boot- Narrow plastic tube on the back of a connector, which supports the fiber.

Breakout cable- Subjacketed single or multiple strands of fiber, underneath an overall outer jacket. Used for point to multipoint installations.

Breakout kit- Set of 900 micron tubing in which 250-micron loose tube fibers are inserted before the installation of connectors. Also called a "furcation kit".

Buffer Coating- see "primary or buffer coating".

Build out box- A known length of fiber, usually 250 or 500 meters, with connectors installed on each end. The fiber is usually contained in a box. When connected to the opposite end of a fiber link from an OTDR, will allow the end connector of the link being tested to be visible on the OTDR trace or display.

Bus configuration- A cabling methodology where a pair of conductors are routed, and network devices can be connected anywhere along the cable route. Cables from devices are not returned to a central location.

Cable- Protective elements and wrappings around fiber optic strands. Typically consisting of an outer jacket, strength member, and inner tubing ("loose tube") or 900-micron plastic jacket applied directly to the fiber strand ("tight tube").

Category 6- Current EIA/TIA standard for copper network and telecommunications cabling within a building. This wire is an unshielded four pair design, with an overall outer jacket. Such cable is also called "Cat 6", or "Cat 6 UTP".

CATV- Acronym for cable television systems.

CCTV- Closed Circuit (security) Television.

Cellophane tape- Standard clear tape that can be used to clean fiber connector ends.

Central strength member- A metal or fiberglass rod, centered in a fiber optic cable, which provides strength and bending protection. Can be used to pull the fiber cable.

Cladding- Silica glass layer surrounding the core of a fiber that is of a higher Index of Refraction (slower speed of light) than the core. Cladding diameters are usually 125 microns. The difference in the speed of light between the cladding and the core helps to keep the light signal within the core.

Cleave- A fiber end that has been broken off cleanly, with a 90 degree face. Cleaves are needed for mechanical and fusion splicing, as well as some types of connector installation.

Cleaver- Fiber optic specific tool that cleaves fiber ends.

Cleaving- Using a specialized tool to break off a fiber so that the end is within one degree of perpendicular. Fibers are cleaved before splicing or installation of pre-polished connectors. A poor cleave will result in a low quality, high loss termination.

Close coupled rays- Light rays in multimode fiber that are traveling nearest the center of the fiber core.

Coaxial cable- A single copper conductor surrounded by insulating materials and shielding of various types. Used in high bandwidth applications such as cable television systems.

Composite cable- Combination of fiber and copper conductors together under a single outer jacket.

Conduit fill- Amount of cables within a conduit. The maximum amount that can be properly placed in a certain sized conduit is regulated by the NEC (National Electric Code).

Connector- Appliance that allows the easy connection and disconnection of fiber links. Common types include the ST, SC, and FC.

Connector set- Two fiber connectors mated with an adapter or barrel, to provide connection between two fiber links.

Connector body- Main part of the connector, the body holds the fiber securely.

Connector loss- Attenuation of the light signal as it passes through two connectors mated in an adapter. This loss is always measured through two connectors mated with an adapter.

Consumables- Items that will be expended during the installation of connectors and splices. They include alcohol wipes, crimp sleeves, glue, and polishing cloths.

Continuity - If a fiber strand is not broken, it is considered to be "continuous". Visible light or laser light testers are commonly used to test for continuity.

Continuous fiber- A fiber strand or link that is not broken. Continuity is often confirmed with a white light or laser tester.

Core- The center of a fiber strand made of the highest grade of silica glass. The core will have a lower Index of Refraction (faster speed of light) than the cladding that surrounds it. The core is where the majority of the signal travels in a fiber strand. Typical core diameters are 7-9 micron (singlemode) or 50 and 62.5 micron (multimode).

Cursor- Movable marker on an OTDR display, which is placed at specific points along the trace to measure losses. Most OTDR's will have two cursers, often labeled "A" and "B".

Dark fiber- Pre-installed fiber strands that are currently not being used. A fiber cable may have six individual fiber strands, with only two currently connected to optoelectronic devices. The other four fibers in this example would be considered "dark".

DBm- Measurement of optical power output of a light source or transmitter, referenced to one milliwatt of light power. 0 dBm equals one milliwatt, -10 dBm is equal to 1/10th of a milliwatt, while 10 dBm equals 10 milliwatt. This measurement is obtained by using an "optical loss" meter, also called a "power" meter.

Dead zone- Portion of an OTDR trace or display immediately to the right of a reflective event, where the display spikes up before coming back to the sloping "back scatter" line. Any "events" occurring within the dead zone will not be individually shown on the OTDR trace or display.

Dead zone box- Pre-made coil of a known length of a single fiber strand with connectors on each end, usually housed in a plastic box. Used to connect between an OTDR and a fiber link, so that the "dead zone" will end within the known length of the fiber in the box, allowing the connector nearest the OTDR to appear on the display or trace.

Decibel (dB)- A mathematic ratio which compares the amount of power input versus the amount of power received. Measurement value of optical loss in fiber optic links. 0 dB equals no loss, -3 dB equals a 50% loss, and -10 dB equals a 90% loss.

Dense Wave Division Multiplexing ("DWDM")- High bandwidth singlemode technology which subdivides the transmission wavelengths between 1550 nm and 1625 nm into 256 separate channels for optical communication.

Dialectric- Cable design which incorporates no metal strength or jacket elements.

Diffusion- Attenuation of light power due to collision with particles, such as fog.

Digital- Communication signals transmitted as "1's" and "0's". Commonly used in telecommunications and computer networks.

Distribution cable- Fiber cable with a quantity of 900 micron jacketed fiber strands, held within an overall aramid yarn wrap and outer jacket. Very commonly used for a variety of uses, including connections of computer rooms and/or patch panels. Typical fiber counts in a distribution cable are six, twelve, twenty-four, or forty-eight strands.

Documentation- Written or electronic recording of fiber optic OTDR, ORL, or loss testing. It is important to retain records of fiber optic tests for later comparisons.

DWDM- Dense Wavelength Division Multiplexing. Using up to 256 separate wavelengths between 1550 and 1625nm to provide multiple signals through one fiber strand. These signals can be in one direction or bi-directional.

Echoes- False indications of reflective events on an OTDR trace or display, caused by reflections from connector pairs and mechanical splices. Very common.

EIA/TIA - Electronic Industry Association/Telecommunications Industry Association. These groups issue standards for copper and fiber optic installation and performance.

EIA/TIA 568- USA standards for the installation of communications cabling within commercial buildings. These standards include the type of materials, methods of installation, maximum lengths of cable runs, and testing procedures.

Electromagnetic Interference (EMI)- Electrical interference caused by motors with spinning armatures, which creates a magnetic field around the electric device.

Electronic Industry Association- Association of computer equipment and cabling manufacturers and corporate users. Involved in the setting of standards in the USA.

Erbium- "Rare earth" element infused into fiber strands within a 1550 nm optical amplifier. When excited by an external laser, the erbium "doped" fiber will transfer optical power to optical signals traveling through the optical amplifier.

Ethernet- Very commonly used protocol or language for computer networks. Various Ethernet speeds are available, from 10 megabits per second to 100 and 1000 megabits per second ("Gigabit Ethernet").

Event- Any deflection, up or down, of an OTDR display or trace away from the downward sloping "back scatter". Events may be "reflective" with an upward spike, indicating a mechanical splice or connector pair. A downward spike is a "non-reflective" event, indicating a fusion splice or bend radius violation.

FC- Screw-in connector style, with a 2.5 mm diameter ferrule. Commonly used in singlemode systems. Fading in popularity.

Ferrule- Tip of a connector, which holds the fiber end securely. Usually 2.5 mm in diameter. Can be made of stainless steel, ceramic, or plastic material.

Fiber cable gripper- Sometimes called a "Kellum's grip", this device has a metal mesh that grips the end of a large diameter fiber cable, and provides a pulling eye for attaching a pull string.

Fiber Jumper- Short fiber link, usually 1 to 3 meters in length. Used to connect two fibers in a telecommunications room or patch panel. Also connected to loss meter and light source for optical loss testing.

Fiber Optic Link- A complete fiber optic path, with a connector on each end of a fiber span. Links may include mid-span splices.

Fiber optic modems- see "optoelectronics".

Field polishing- Installation of connectors at the job site by stripping the fiber, gluing it into a connector, and polishing the fiber down to the ferrule tip of the connector.

Fixed attenuators- Usually adapters with a plastic or metal screen, which will reduce the amount of optical signal passing through a connector pair. Can be obtained with specific amount of loss at a particular wavelength, such as "-10 dB at 1310nm". Such devices are highly reflective.

Flat Polish- Obsolete finish of a connector end, providing a flat fiber end with no radius.

Foot- .31 of a meter

Foot markers- Numbers stamped on the sides of most fiber cables. By subtracting the number on one end of a cable from that on the other, the length of the outer jacket of the cable can be determined.

Free Space Optics- Communications network using optical transmitters and receivers, with the signal being sent through the air. Transmitters and receivers must have "line of sight" to function properly.

Fresnel Effect- Reflection of light signals as they pass from one medium (material) to another. Up to four percent of a light signal's power will be reflected as the light passes between materials.

Furcation kit- see "breakout kit".

Fusion splice- Electrically welded joint between two fiber strands. Provides lowest loss connection with no back reflection. Often used in singlemode fiber links.

Fusion splicer- Special device that performs fusion splices. Usually has settings to splice multimode or singlemode fiber.

Gainer- Fusion splice that appears on an OTDR trace or display as an increase in optical power. This is caused by splicing fibers with different Mode Field Diameters. When tested with the OTDR from the opposite direction, the "gainer" will appear to have a large loss.

Gel blocking- A viscous fluid injected into loose tube fiber cables to repel any water entering.

Gigabit Ethernet- Computer network protocol that can transmit data at a rate of 1000 megabits per second.

Gigabit mandrel- A 21-millimeter cylinder, with five wraps of a launch cable around it. Required by the EIA/TIA standards to test multimode fiber for its usability with Gigabit Ethernet laser signal transmissions.

Graded Index- Multimode fiber strand with a core composed of multiple layers of silica glass with increasing Indexes of Refraction, so that the "slowest" glass is in the very center and the "fastest" glass is on the outside of the core. This construction reduces "pulse spreading". Most multimode fiber is Graded Index.

Heat shrink protector-Usually clear heat shrink tubes, normally 60 mm in length, with a metal strength bar incorporated. Used to protect completed fusion splices.

Home run wiring- cabling method where each cable is brought back to a central place for termination or cross-connection. No intermediary connections are used.

Hum bars- Horizontal interference on a television or CCTV monitor.

Hybrid cable- Fiber cable with both singlemode and multimode fiber strands under one jacket.

Hybrid adaptor- Adapters that mate connectors with different body types. As the FC, ST, and SC connector all have a 2.5 mm ferrule, such adapters as ST-SC, SC-FC, and ST-FC are available.

Hybrid jumpers- Fiber jumpers with different types of connectors on each end. Commonly used for optical loss testing.

Index of Refraction- The speed of light in a vacuum divided by the speed of light in a material, such as silica glass. This number will vary between 1.4 and 1.59 in fiber optics. This value is used in setting up an OTDR test to display the accurate length of a fiber link.

Indoor/Outdoor cable- Fiber cable that is rated for indoor installation, with the strength and protection needed for outdoor installation. This cable will be an all dialectric design, having no metal elements.

Index matching gel- Viscous clear jelly-like substance, used in mechanical splices to reduce back reflection and to improve light signals' passing through.

Industrial Ethernet- Use of Ethernet communication protocols in industrial applications, in places such as factories, oil platforms, and other facilities. Often carried on fiber optic strands.

International Telecommunications Union ("ITU")- Worldwide communications standard setting organization.

Jitter- Signaling problem, occurs with laser transmitters in fiber optics. Can be caused or increased by excessive back reflection.

Kevlar- see "aramid yarn".

Kilometer- 1000 meters, 6/10's of a mile.

Laser- High-powered light source used in high bandwidth singlemode and multimode fiber systems.

Laser tester- A visible laser, usually 660nm, used to troubleshoot fiber links and jumpers.

Launch cables- fiber jumpers used for loss testing.

Least squares approximation ("LSA")- OTDR measurement setting, normally used for the measurement of connector pairs or splices. When set to LSA, software in the OTDR provides a calculation of the loss of a particular event while eliminating the distance loss from the length of the "dead zone" of the event.

LED- Light Emitting Diode. Light source used in multimode fiber transmitters.

Light inject and detect ("LID")- Active alignment technology used in some fusion splicers.

Light source- Constant wavelength emitter used in loss testing of fiber optic links. Can be an LED for multimode, or a laser for singlemode testing.

Lightwave converters- see "optoelectronics".

Link- term for a completed fiber optic section, with a connector on each end. May include mid-span splices.

Loose-coupled rays- Rays of light traveling in a multimode fiber that bounce from one side of the core/cladding boundary to the other. These rays will have to travel the furthest distance to get from one end of a fiber link to the other.

Loose tube- Fiber cable with non-jacketed individual strands that are held within 3 mm tubes underneath an overall outer jacket. Usually used in outdoor applications.

Loss Meter- Calibrated device that measures optical power received. After being "zeroed", can also provide measurements of optical loss in a fiber link. Also called a "power meter".

Loss Meter Set- Loss meter and light source. Both devices are needed for optical loss testing.

Loss testing- Using a light source and power meter set to test a fiber optic link for attenuation.

Mandrel wrap- see "Gigabit mandrel".

Manual alignment- Original system for alignment of fibers for fusion splicing. The technician visually aligns the fibers before fusing.

Mass fusion splicer- Specialized splicer for ribbon fiber that welds all twelve fibers at the same time.

Maximum attenuation- The maximum amount of optical loss that an optoelectronic set (transmitter and receiver) can withstand without degradation of performance.

Mechanical splice- An appliance that hold two cleaved fiber ends together, providing an optical connection. Usually used with multimode fiber. These splices will have higher loss and back reflection when compared to a fusion splice.

Media converters- Electronic devices that convert optical signals to their electrical component, and visa versa. Generally protocol specific.

Meter- Length measurement equal to 39.37 inches. Also see "loss meter".

Micro bend- Pinching or tightly placed pressure on a fiber optic cable or strand. Micro bends can cause increased optical loss in a fiber link. Plastic tie wraps that bind a fiber tightly can cause micro bends.

Micron- One millionth of a meter.

Mini OTDR-An OTDR that takes a picture of a fiber link, and produces a display. "Mini OTDR's" are not "real time", and do not display changes in a fiber link's condition as they take place.

Mode Field Diameter ("MFD")- The area in a singlemode fiber where the optical signal travels. Typically, this includes the core and 10 to 20% of the cladding immediately surrounding the core.

Multimode- A fiber core with multiple paths for light to travel. Multimode means "multiple path". Typical multimode core diameters are 62.5 and 50 microns.

Multiplexing- Transmitting and receiving multiple separate signals through a single fiber strand.

Multiplexer- Combines multiple separate signal streams onto one or two fiber strands. Used to reduce the number of fiber strands needed for communications between two points.

Nanometer- One billionth of a meter. Also expressed as 1/1,000,000,000th of a meter.

Narrowband WDM- Narrowband Wavelength Division Multiplexing. Uses multiple wavelengths that are near 1550nm to transmit multiple signals on a single fiber strand. These signals can be in one direction or bi-directional.

Nation Fire Prevention Association ("NFPA")- USA standards body for fire prevention issues.

National Electric Code ("NEC")- Standards for electrical and cabling installation in the USA.

Noise Floor- On an OTDR trace or display, the area past the end of the fiber when the image drops below the level of the backscatter trace. Large upward spikes in the noise floor are an indication that there may be "echoes" in the OTDR trace.

Non-Reflective Events-Fusion splices or bend radius violations on an OTDR trace or display. These events are noted because they spike downward before returning to the backscatter.

Optical Amplifiers- Optoelectronic devices that boost an optical signal without converting the signal into its electrical component.

Optical budget-Alternatively, the maximum amount of optical loss (measured in dB) that a particular set of optoelectronic devices can withstand and provide optimal performance, or, the calculation of the amount of loss expected in a planned fiber optic link installation.

Optical Fault Locator ("OFL")- An optical time domain reflection tester that provides an alphanumeric readout of events, without a linear trace.

Optical matching gel- viscous gel used in mechanical splices to reduce back reflection and to increase throughput of optical signals.

Optical Power- Measurement of the output of a fiber optic transmitter or light source.

Optical Return Loss Tester("ORL")- Meter that sends a constant wavelength of laser light into a fiber link, and measures the amount of optical return loss.

Optical Return Loss ("ORL")- Measurement of the amount of optical energy reflected back to the transmitter.

Optical Time Domain Reflectometer (OTDR)- Device that provides a graphic display of a fiber link, providing information about fiber quality, length, and optical loss from connector sets, splices, and installation errors.

Optoelectronics- Electronic devices that convert electronic signals (voice, data, or video) into light signals injected into a fiber strand, and visa versa.

OTDR trace- Printed or displayed "picture" of a fiber optic link.

Outside plant- Cabling installed outside of buildings.

Profile Alignment System ("PAS")- Profile Alignment System. One of the technologies used to automatically align cleaved fiber ends in a fusion splicer. PAS uses lights, cameras, and software to align the claddings of the two fiber ends.

Patch Panel- Location where various fiber cables are cross-connected with jumper cables.

PC- Physical Contact. Type of end finish for connectors, provides a slightly round fiber tip. Used for multimode and singlemode. Most common type of connector finish.

Pigtail- Factory assembled fiber optic connector with 1-5 meters of fiber cable attached.

Plenum- A drop ceiling that is being used as an air return for a heating, ventilation, and air conditioning (HVAC) system. There is no separate ductwork in a plenum; the entire cavity above the drop ceiling provides an air passage. Common in commercial buildings.

Power Meter- see "loss meter".

Precision "V" groove- Fusion splicer alignment technology.

Precision Cleaver- Tool that provides cleaves with high accuracy and high yield.

Pre-made cable- Factory made fiber cables with the connectors already installed on both ends.

Pre-polished connectors- Connectors that are field installed by cleaving a stripped fiber end, inserting it into the connector, and crimping. A pre-polished stub of fiber is installed in the ferrule, making polishing by the technician unnecessary.

Primary or buffer coating- Plastic coating over the core and cladding in a fiber strand. Provides strength and additional size for manipulation. Usually 250 or 500 microns in diameter. Removed from the fiber strand during the stripping process.

Protocols- Various computer languages, such as Ethernet or RS-232, that facilitate communications between computers and other devices.

Pulling Strength- The amount of pulling force, measured in pounds or kilograms, that a cable can withstand during installation without damage.

Pulse Spreading- Spreading of signals over time in multimode fiber. Caused by the multiple paths available for optical signals. Primary cause for the distance limitations inherent in multimode fiber.

Pulse Width or Duration- OTDR adjustment or selection of the amount of time that the OTDR's laser is turned on and off during testing. Longer pulse widths provide better definition in long fiber links; also will increase the size of the "dead" zones. Some OTDR's will automatically set the pulse width for the best possible image.

Raceway- Conduits or trays used to hold or support fiber and/or copper cabling.

Radio Frequency Interference (RFI)- Electronic emissions from electrical devices.

Rayleigh scattering- The scattering of light energy as it passes through the core of a fiber strand, due to the light wave electrons colliding with non-glass molecules, most often water.

Real time OTDR- An optical time domain reflectometer that provides a display in real time. Often used to test fusion splices as they are being performed. Most expensive type of OTDR.

Receiver- Optoelectronic device that receives optical signals through a fiber link from a transmitter, and converts them into their digital or analog electrical state.

Reflective Event- An upward spike on an OTDR's display or trace. The upward slope indicates light energy being reflected back toward the OTDR. Mechanical splices and connector sets will produce a reflective event.

Regenerator- Converts a fiber optic signal into its electrical component, and then back into an optical transmission. Used to reamplify weakened optical signals in long distance networks.

Repeatability- Standards required optical loss test, where connectors are reconnected three times. There should be no more than .1dB difference between the tests.

Retention mechanism- Epoxy glue or metal crimp ring used to attach the jacket of a fiber strand and/or strength member to the body of a connector.

RG6- Copper coaxial cable used for CATV applications.

Ribbon fiber- High count, small size fiber strand package. Generally used in long distance applications.

Rip String- Cord built into certain types of fiber cable that can be pulled to cut outer jacket materials. Installation aid.

Riser- Cable raceways that travel from floor to floor in a building.

Roll test- Testing of a reel of fiber before it is installed. Tests may include OTDR, visible light, or optical loss.

SC- Square connector body with a 2.5 mm ferrule. Very commonly used in computer network applications. Can be multimode or singlemode. Second most popular connector behind the ST. Most connector installation kits will include the tools to install the SC. Sometimes called the 'stick and click", as this connector is mated to its adapter with an insertion until a "click" is heard.

Shielded cable- Copper cabling with a metallic foil or screen surrounding the conductive elements. The shielding provides some level of rejection of RFI and EMI, which can affect electrical signaling.

Silica glass- Type of material used to manufacture most common fiber optic strands.
Fiber optic glass is of the highest purity and quality.

Singlemode fiber- Strands with a core of 7-9 microns of faster light speed silica glass surrounded by a cladding (usually 125 microns) of slower light speed silica glass. Singlemode is used with 1310 and 1550 nm laser transmitters, and has the lowest attenuation over distance of any fiber type. This type of fiber has the highest bandwidth capability.

Slack cable- Excess lengths of fiber cable. Industry recommendations are that a minimum of 10 meters of slack cable be provided for each end of a multi-strand fiber cable installation. Slack cable should be stored so that the bend radius of the fiber is not violated.

Speed of light- 186,000 miles per second in a vacuum. Slower in silica glass fiber optic strands. Dividing the speed of light in a specific fiber by the speed of light in a vacuum equals the "Index of Refraction" of that fiber.

Spike- Sharp movement, upward or downward, on an OTDR trace.

Splice- Joining of two separate fiber strands into one continuous strand. Used to join separate fiber rolls, attach pigtail splices, and to join different types of fiber cable, such as an indoor distribution cable to an outdoor loose tube type. Splices can be mechanical or fusion. Mechanical splices are often used with multimode fiber, while singlemode fiber is most often fusion spliced.

Splice enclosure-Box or container that holds splices. These enclosures may be wall mounted, rack mounted, pedestal, or direct burial. The container will have a method for securely holding the splices in their protectors, as well as cable management hooks or holders to reduce the potential of excessive fiber bending within the enclosure.

Splice loss- Optical loss created by mechanical and fusion splices. Can be measured with a loss meter set or OTDR. Industry standards call for .3dB or less of loss for a splice, whether mechanical or fusion, multimode or singlemode. Singlemode specifications will often call for .1 dB per splice or less. Mechanical splices will have higher amounts of loss than comparable fusion splices. Fusion splices routinely will test to less than .1 dB.

Splice tray- A separate splice holder that will fit into a splice enclosure or other box. Secure methods of holding the splices and cable management hardware are included.

Splicing pod- See "splice enclosure".

ST- Round connector body with a 2.5 mm ferrule. Can be singlemode or multimode. Most popular style of fiber optic connector. Developed by AT&T in the 1980's. Sometimes called the "stab and twist", as the connector is mated to the adapter by inserting the connector and turning the outer shell.

Standards- Created by industry committees, these are published documents providing parameters of installation, products, and performance.

Star configuration- See "home run wiring".

Static- When a fiber cable is not subject to pulling forces.

Step Index- Multimode fiber with a uniform type of silica glass throughout the core. Step index fiber will exhibit more pulse spreading of optical signals than a graded index multimode fiber. Obsolete type of fiber that has been superseded by graded index fiber strands. Still used in nuclear power plants.

Strand- Multimode or singlemode fiber without any jacketing material. Includes the core, cladding, and primary or "buffer" plastic coating layers.

Strength element- Materials included under the outer jacket of a fiber optic cable to provide strength and protection. Commonly aramid yarn. Used to pull fiber cable by tying the pulling rope or tape to the strength element.

Strength member- see "strength element".

Stripping- Removing the 900 micron plastic jacket (if present) and 250 micron buffer coating from a fiber end, in preparation for splicing or connector installation.

Telephone Industry Association- Group of telecommunications manufacturers, providers and users. Forms committees to develop industry standards.

Tensile test- Applying a small amount of pulling pressure to a fusion splice after welding. If a fusion splice is made improperly, it will easily break with little pulling effort. Often this test is performed automatically by the fusion splicer; this test can also be performed by hand.

Test Jumper- see "launch cable".

Tight tube- Fiber cable type with 900 micron diameter plastic jacketing applied directly to the fiber strands. Zip cords and distribution cable are typically tight tube design. Generally used indoors.

Total internal reflection- Property by which the light signal stays within the core of a fiber strand, because of the higher speed of light in the core glass as compared to the cladding.

Transceiver- Optoelectronic device that both transmits and receives optical signals.

Transition- During planning and installation, the connection of one type of fiber cable to another. Typically outdoor fiber will be transitioned to indoor fiber. Connection of the different fiber types may be by connector pairs or splices. Usually such a transition will require a splice enclosure or box.

Transmitter- Optoelectronic device that converts digital or analog electrical signals into an optical output.

Tunable laser- High bandwidth transmission laser that can be adjusted to different wavelengths within a band. Used in Dense Wave Division Multiplexing networks. Singlemode devices.

Two point loss- Measurement of loss between the two cursers on an OTDR trace or display. Can be used to measure quality of fiber. When used to measure splice loss, this method will include the loss of the fiber length in the "dead zone", adding a small amount of additional loss to the measurement.

Underwriters' Laboratories ("UL")- US product safety testing body.